Loudspeakers were invented over 150 years ago, but the loudspeakers used today are still based on the same ideas. Traditionally, good sound quality has been obtained by using expensive materials in the loudspeakers and by allowing them to be big. However, nowadays loudspeakers are wanted in applications such as mobile phones and tablets where size and weight are limited and there is a desire to decrease production costs. Special small loudspeakers, known as micro loudspeakers or microspeakers, have been developed for this purpose. However, due to restrictions in size and manufacturing costs, their sound quality can be relatively poor.
One approach to overcoming this challenge is to use digital signal processing and active control to compensate for the poor quality. That is, a digital signal processor (DSP) may be used to adapt the input audio signal such that, once passed through the loudspeaker, a desired output is achieved. However, such techniques require the application of an accurate model in order to be effective.